Middle distillate

ABSTRACT

MIDDLE DISTILLATE OF IMPROVED POUR POINT CONTAINING A POUR POINT DEPRESSANT AMOUNT OF A C14-C26 SATURATED CARBOXYLIC ACID ESTER OF A POLYHYDRIC ALCOHOL HAVING FROM 4 TO 8 HYDROXY GROUPS.

United States Patent oat-e 3,672,854 Patented June 27, 1972 3,672,854MIDDLE DISTILLATE Robert H. Rosenwald, Western Springs, and AlexanderGaydasch, Chicago, Ill., assignors to Universal Oil Products Company,Des Plaines, Ill. No Drawing. Filed Dec. 3, 1969, Ser. No. 881,895

Int. Cl. C] 1/18 l J.S. Cl. 44-66 3 Claims ABSTRACT OF THE DISCLOSUREMiddle distillate of improved pour point containing a pour pointdepressant amount of a (D -C saturated carboxylic acid ester of apolyhydric alcohol having from 4 to 8 hydroxy groups.

BACKGROUND OF THE INVENTION Middle distillates are defined as petroleumdistillates containing components boiling above the range of gasolineand having an end boiling point of not above about 750 F., and are sodefined in the present specification and claims. In one embodiment themiddle distillate also may include components boiling within thegasoline range and, in this embodiment, the middle distillate will boilwithin the range of from about 250 to about 750 F. In another embodimentthe middle distillate will have an initial boiling point above gasolineand thus will boil within the range of from about 400 to about 750 F.

The middle distillate is a liquid mixture of hydrocarbons and, uponcooling, some of them crystallize to form a waxy precipitate. Thesecrystals become active centers for further crystallization, with theresult that the distillate congeals and loses its free flowingproperties. The temperature at which this occurs is defined as the pourpoint and is of importance to petroleum refiners and users of the oil inorder that the distillate may be pumped or syphoned readily fortransportation or use.

Various means have been proposed heretofore to improve the pour pointproperties of the middle distillates. In one method this has taken theform of additional processing steps at the refinery, such as solventextraction to remove the components believed to cause crystallization.In another method various additives have been proposed, originally basedupon those which have been found effective in lubricating oils. However,it has been found that pour point depressants which are satisfactory inlubricating oils are not generally effective in middle distillates.

DESCRIPTION OF THE INVENTION As hereinbefore set forth, the middledistillate will be within the boiling range of from about 250 to about750 F. Illustrative middle distillates include kerosene, fuel oil,diesel oil and other middle distillates used for combustion or ascleaning oils for cleansing metallic equipment. In another embodimentthe middle distillate is an electrical insulating oil which is used intransformers, circuit breakers, etc. In still another embodiment themiddle distillate may comprise a conventional hydraulic oil. In stillanother embodiment the middle distillate may comprise an intermediateoil which is awaiting further processing as, for example, light cycleoil from catalytic cracking is being stored or transported prior torecycle to the catalytic cracking or sent to another process.

Regardless of the particular middle distillate, it is readily apparentthat the distillate must be free flowing at all temperatures encounteredin the transportation, storage and use thereof. The pour pointproperties of the middle distillate are improved in accordance with thepresent invention by incorporating a particular carboxylic acid ester ofa particular polyhydric alcohol.

In one embodiment the present invention relates to a middle distillateof improved pour point containing a pour point depressant amount of a C.,C saturated carboxylic acid ester of a polyhydric alcohol having from4 to 8 hydroxyl groups.

In a specific embodiment the present invention relates to fuel oilcontaining sorbitan tristearate.

In another specific embodiment the present invention relates to fuel oilcontaining pentaerythritol monw stearate.

As hereinbefore set forth, the pour point properties of the middledistillate are improved by incorporating therein a particular carboxylicacid ester of a particular polyhydric alcohol. The particular carboxylicacid used in forming the ester must be a saturated acid having fromabout 14 to about 26 carbon atoms. As will be illustrated in theappended examples, ester formed from unsaturated acid was found to beineffective for the purpose. Also, the ester prepared from C fatty acidwas ineffective. Saturated carboxylic acids containing 14 to 26 carbonatoms include tetradecanoic acid, pentadecanoic acid, hexadecanoic acid,heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoicacid, heneicosanoic acid, docasanoic acid, tricosanoic acid,tetracosanoic acid, pentacosanoic acid and hexacosanoic acid. The acidpreferably is straight chain but may contain one or two lower (1 to 4carbon atoms) side chains. Conveniently these acids are derived fromfatty acids and thus include myristic, palmytic, stearic, arachidic,behenic, lignoceric and cerotic. A number of these acids are availablecommerically as a mixture and, as another advantage to the presentinvention, the lower cost mixed acids may be used in preparing the esterfor use in the present invention.

As hereinbefore set forth, the polyhydric alcohol contains from 4 to 8hydroxyl groups. It was found that esters of glycol or glycerol wereeither of no activity or of very little activity in improving the pourpoint of the middle distillate. In contrast, esterification ofpentaerythritol (containing 4 hydroxyl groups) produced very effectivepour point depressants. Conveniently the polyhydric alcohols comprisecarbohydrates and thus include glucose, fructose, mannose, glactose,allose, altrose, talose, gulose, idose, as well as disaccaridesincluding sucrose, lactose, maltose, etc. In another embodiment thepolyhydric alcohol is sorbitol and, in fact, a particularly preferredester for use in the present invention is sorbitan stearate. During theesterification of sorbital, cyclization occurs with the formation of amixture of polyhydroxy 5 and 6-member oxygen-heterocyclic rings. Alsouseful as polyhydric alcohols are the dimers as, for example,dipentaerythritol, poly and preferably di-oxygen-heterocyclic ringcompounds having 4 to 8 hydroxyl groups. Here again it is understoodthat a mixture of polyhydric alcohols may be used in the preparation ofthe ester.

The ester for use in the present invention may be obtained from anysuitable source or prepared in any suitable manner. A number of sorbitanesters meeting the requirements of the present invention are availablecommercially as Span 40 (sorbitan monopalmitate), Span (sorbitanmonostearate), Span (sorbitan trist earate), Armotan MS (sorbitanmonostearate), Drustan 60 (sorbitan monostearate), Drustan 65 (sorbitantristearate), etc. When desired, the ester may be prepared by directesterification of the alcohol with acid, by reaction with acid halides,by transesterification or in any other suitable manner. These methodsare well known in the art and need not be described in detail herein.(Either the crude reaction product or selected fraction thereof may beused, depending upon the effectiveness for the purpose.)

The ester formed in the above manner is incorporated in the middledistillate in a suflicient concentration to lower the pour point of themiddle distillate to a satisfactory degree. The concentration of ester,may be within the range of from about 0.001% to about 1% but generallyis within the range of from about 0.01% to about 0.5% by weight of themiddle distillate. When desired, the ester may be prepared as a solutionin a suitable solvent which conveniently comprises hydrocarbon,including aromatics such as benzene, toluene, xylene, cumene, etc. orparafiins including decane, undecane, dodecane, tridecane, tetradecane,pentadecane, etc. but generally comprises a mixture such as high boilingnaphtha, kerosene, a portion of the middle distillate, etc. It isunderstood that the ester may be used in conjunction with otheradditives normally added to middle distillates which additive will varywith the particular middle distillate and may comprise one or more ofantioxidant, corrosion inhibitor, cetane improver, dye, metaldeactivator, etc.

The following examples are introduced to illustrate the novelty andutility of the present invention but not with the intention of undulylimiting the same.

EXAMPLE I A number of esters were evaluated as pour point depressants intwo different middle distillates as follows:

Middle distillate A is a commercial No. 2 fuel oil having an initialboiling point of 428 F. an end boiling point of 677 F, and a pour pointof F.

Middle distillate B is a light cycle oil from a'commer- 'cil catalyticcracking unit. This distillate has an initial boiling point of 397' R,an end boiling point of 650 I and a pour point of 10 F.

- The pour points were determined by ASTM D97-57 method, which is astandard method for determining pour points. The results reported in thefollowing table are the pour point depression, which is the differencebetween the pour point of the blank or control distillate (withoutadditive) and the pour point of the distillate containing the additive,reported in F.

Unless otherwise indicated, the ester was incorporated in the middledistillate in a concentration of 1000 p.p.m. (pin-ts per million) (0.1%by weight) of the middle disti ate.

From the data in the above table it will be noted that the extent ofpour point depression varied with the different middle distillates.Accordingly the particular pour point depressant will be selected withreference to the particular middle distillate in which it is to be used.

EXAMPLE II The data reported in Example I were on the basis of 1 000p.p.m. of the pour point depressants. The sorbitan tristearate also wasevaluated in lower concentrations. In a concentration of 500 p.p.m., thepour point depressions were 30 and in distillates A and B respectively.At a .4 concentration of 250 p.p.m., the pour point depressions were 25in both distillates. This demonstrates that the lesser amounts of esterwere effective in these middle distillates.

EXAMPLE III Sorbitan tristerate also was evaluated in a commercialdiesel fuel oil having an initial boiling point of 377 R, an end boilingpoint of 655 -F. and a pour point of 5 F. when used in a concentrationof 1000 p.p.m., sorbitan tristearate served to effect a 20 F. pour pointdepression.

EXAMPLE -IV -As hereinbefore set forth, the ester must be a saturatedcarboxylic acid ester. This is demonstrated in tests made with sorbitanmonooleate and sorbitan trioleate. When these esters were evaluated inmiddle distillates A and B at a concentration of 1000 p.p.m. there wasno depression of pour point in all cases except a 5 F. depression indistillate A when using the sorbitan monooleate.

EXAMPLE V As hereinbefore set forth, the carboxylic acid used inpreparing the ester must contain at least 14 carbon atoms. This isdemonstrated in another series of tests in which sorbitan monolauratewas evaluated in a concentration of 1000 p.p.m. in distillates A and B.There was no depression in pour point in either of these evaluations.Thus, the ester formed from lauric acid (12 carbon atoms) was noteffective in lowering the pour point of the middle distillate.

EXAMPLE VI As hereinbefore set forth, the polyhydric alcohol used informing the ester should contain at least 4 hydroxyl groups. This isdemonstrated in another series of tests in which ethyleneglycoldistearate, diethyleneglycol distearate, glyceryl monostearate andglyceryl tristearate were each evaluated in a concentration of 1000p.p.m. in middle distillates A and B. The ethylene glycol distearate dideffect a pour point depression of 5 F. in middle distillate B.Diethylene glycol distearate was of no benefit in either of the middledistillates. Glyceryl mono'stearate showed a 5 F. pour point depressionin distillate B. No benefit in distillate A. Glyceryl tristearate showeda 5 F. pour point depression in distillate A and a 15 F. depression indistillate B. It is apparent that these esters are practically of noeffect in reducing the pour point.

EXAMPLE VII The ester of this example is a mixture of esters formed froma mixture of arachidic and behenic acids and sorbital. The mixed estersare added in a concentration of 1000 p.p.m. to No. 2 fuel oil and servesto reduce the pour point thereof.

EXAMPLE VIII Sorbitan myristate is incorporated in a concentration of750 p.p.m. in commercial kerosene and serves to lower the pour pointthereof sufficiently to avoid any pumping problems at temperaturesnormally encountered in the transpontation of the kerosene.

We claim as our invention:

1. A fuel oil comprising a No. 2 fuel oil middle distillate and a C -Csaturated carboxylic acid ester of a polyhydric alcohol having from 4 to8 hydroxyl groups, said ester in a pour point depressant concentrationof from 0.01% to about 0.5% by weight.

2. A light cycle oil comprising a light cycle oil middle distillate anda C -C saturated carboxylic acid ester of a polyhydric alcohol havingfrom 4 to 8 hydroxyl groups, said ester in a pour point depressantconcentration of from 0.01% to about 0.5% by weight.

3. A fuel oil comprising kerosene and a C -C saturated carboxylic acidester of a polyhydric alcohol having from 4 to 8 hydroxyl groups saidester in a pour point depressant concentration of from 0.01% to about0.5% by weight.

References Cited UNITED STATES PATENTS 2,527,889 10/1950 Moore et a1.4466 2,560,202

DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner US.Cl. X.R.

6/1951 Zimmer et a1. 4466 10 44 70 I

